Hip joint device and method

ABSTRACT

A medical device for implantation in a hip joint of a patient is provided. The medical device is adapted to be fixated to the femoral bone of the patient. The medical device comprises an inner and an outer surface, wherein a contacting portion of said inner surface is spherical and adapted to face the center of the hip joint when said medical device is implanted, and wherein said medical device is adapted to receive a prosthetic replacement for the caput femur fixated to the pelvic bone having a spherical portion. The medical device comprises at least one extending portion, extending said contacting portion of said inner surface such that said at least one extending portion clasps said spherical portion of said prosthetic replacement for the caput femur, such that said spherical portion is restrained in said medical device.

This application is the U.S. national phase of International ApplicationNo. PCT/SE2010/050832, filed 12 Jul. 2010, which designated the U.S. andclaims the benefit of U.S. Provisional Nos.: 61/229,738 filed 30 Jul.2009; 61/229,739 filed 30 Jul. 2009; 61/229,743 filed 30 Jul. 2009;61/229,745 filed 30 Jul. 2009; 61/229,746 filed 30 Jul. 2009; 61/229,747filed 30 Jul. 2009; 61/229,748 filed 30 Jul. 2009; 61/229,751 filed 30Jul. 2009; 61/229,752 filed 30 Jul. 2009; 61/229,755 filed 30 Jul. 2009;61/229,761 filed 30 Jul. 2009; 61/229,767 filed 30 Jul. 2009; 61/229,778filed 30 Jul. 2009; 61/229,786 filed 30 Jul. 2009; 61/229,789 filed 30Jul. 2009; 61/229,796 filed 30 Jul. 2009; 61/229,735 filed 30 Jul. 2009;and which claims priority to Swedish Application Nos.: 0900981-2 filed10 Jul. 2009; 0900957-2 filed 10 Jul. 2009; 0900958-0 filed 10 Jul.2009; 0900959-8 filed 10 Jul. 2009; 0900960-6 filed 10 Jul. 2009;0900962-2 filed 10 Jul. 2009; 0900963-0 filed 10 Jul. 2009; 0900965-5filed 10 Jul. 2009; 0900966-3 filed 10 Jul. 2009; 0900968-9 filed 10Jul. 2009; 0900969-7 filed 10 Jul. 2009; 0900970-5 filed 10 Jul. 2009;0900972-1 filed 10 Jul. 2009; 0900973-9 filed 10 Jul. 2009; 0900974-7filed 10 Jul. 2009; 0900976-2 filed 10 Jul. 2009 and 0900978-8 filed 10Jul. 2009, the entire contents of each of which are hereby incorporatedby reference.

TECHNICAL FIELD

The present invention relates generally to medical devices forimplantation in a hip joint

BACKGROUND ART

The hip joint is a synovial joint, joining the pelvis to the proximalportion of the femoral bone. Synovial joint are the most common types ofjoint in mammals, and are typical of nearly all limb joints. Thecontacting surfaces of said the pelvic, the acetabulum, and thecontacting surface of the femoral bone, the caput femur, are smooth androunded, and covered by articular cartilage. A synovial membrane,encapsulates the joint, forming a hip joint cavity, which containssynovial fluid. Outside the synovial membrane is a fibrous capsule andligaments, forming an articular capsule.

There are both natural and pathological processes leading todeteriorated joint function. With age and wear, the articular cartilagebecomes less effective as a shock absorber and a lubricated surface.Different degenerative joint diseases, such as arthritis,osteoartrithis, or osteoarthrosis, accelerate the deterioration.

Hip joint O steoarthritis is a syndrome in which low-grade inflammationresults in pain in the hip joints, caused by abnormal wearing of theCartilage that acts as a cushion inside if the hip joint. This abnormalwearing of the cartilage also results in a decrease of the jointslubricating fluid called Synovial fluid. Hip joint O steoarthritis isestimated to affect 80% of all people over 65 years of age, in more orless serious forms.

The present treatment for hip osteoarthritis comprises NSAID drugs,local injections of Hyaluronic acid or Glucocorticoid to helplubricating the hip joint, and replacing part of the hip joint with aprosthesis through hip joint surgery.

The replacing of parts of the hip joint is one of the most commonsurgeries to date performed at hundreds of thousands of patients in theworld every year. The most common method comprises placing a metalprosthesis in Femur and a plastic bowl in Acetabulum. This operation isdone through an incision in the hip and upper thigh and through FasciaTata and the lateral muscles of the thigh. To get access to the joint,the supporting Capsule attached to Femur and Ilium needs to bepenetrated, making it difficult to get a fully functional joint afterthe surgery. Femur is then cut at the neck with a bone saw and theprosthesis is placed in femur either with bone cement or withoutAcetabulum is slightly enlarged using an Acetabular reamer, and theplastic bowl is positioned using screws or bone cement.

The complications after hip joint surgery includes dislocation of thehip joint and loosening of the prosthesis from its fixation in thefemoral bone. The loosening and/or dislocation of the prosthesis couldbe induced by an abnormal strain being placed on the hip joint from e.g.the patient falling or making a rapid movement of the hip, or by abodily macrophage reaction.

SUMMARY

A medical device for implantation in a hip joint of a patient isprovided. The medical device is adapted to be fixated to the femoralbone of the patient. The medical device comprises an inner and an outersurface, wherein a contacting portion of said inner surface is sphericaland adapted to face the center of the hip joint when said medical deviceis implanted, and wherein said medical device is adapted to receive aprosthetic replacement for the caput femur fixated to the pelvic bonehaving a spherical portion. The medical device comprises at least oneextending portion, extending said contacting portion of said innersurface such that said at least one extending portion clasps saidspherical portion of said prosthetic replacement for the caput femur,such that said spherical portion is restrained in said medical device.

According to one embodiment, the medical device is adapted to receive aprosthetic replacement for the caput femur having a spherical portion,wherein said prosthetic replacement for the caput femur is adapted to befixated to the pelvic bone by a connection via an elongated portionfixated to said spherical portion of said prosthetic caput femur. Theinner surface comprises an equator line, being the largest circularcircumference of said inner contacting surface, being a surface adaptedto be in contact with said caput femur, or prosthetic replacementtherefor, and the at least one extending portion passes beyond saidequator line, such that the end portion of said contacting portion ofsaid inner surface forms a circular extension line having a smallercircumference than said equator line. The at least one extending portioncircumferentially extends discontinuously along said equator line, suchthat a portion of said elongated member can be placed between saidextension line and said equator line.

A medical device for implantation in a hip joint is further provided.The medical device is adapted to be fixated to the femoral bone andreceive a prosthetic replacement for the caput femur having a sphericalportion, wherein said prosthetic replacement for the caput femur isadapted to be fixated to the pelvic bone by a connection via anelongated portion fixated to said spherical portion of said prostheticcaput femur. An inner surface comprises an equator line, being thelargest circular circumference of said inner surface, at least oneextending portion passes beyond said equator line, such that the endportion of said contacting portion of said inner surface forms acircular extension line having a smaller circumference than said equatorline, and said at least one extending portion circumferentially extendsdiscontinuously along said equator line, such that a portion of saidelongated member can be placed between said extension line and saidequator line.

According to one embodiment, said extension line is placed dorsal to theequator line, when the medical device is implanted.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, dorsal to the right-left axisof pelvis when being in the defined base position (further disclosedwith reference to FIG. 1b ).

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, dorsal to the coronal pelvisplane PXY and proximal to the horizontal pelvis PXZ plane when being inthe base position.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, dorsal to the coronal pelvisplane PXY and distal to the horizontal pelvis PXZ plane when being inthe base position.

According to one embodiment, one extending portion extendscircumferentially along said equator line dorsal to the coronal pelvisplane PXY and proximal to the horizontal pelvis PXZ plane, and oneextending portion extends dorsal to the coronal pelvis plane PXY anddistal to the horizontal pelvis PXZ plane when being in the baseposition.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, in the proximal quadrant ofthe equator line when being in the base position.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, in the distal quadrant of theequator line when being in the base position.

According to one embodiment, two extending portions extendscircumferentially along said equator line, in the distal and proximalquadrant thereof when being in the base position.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, in the proximal and dorsalquadrant thereof when being in the base position.

According to one embodiment, said at least one extending portion extendscircumferentially along said equator line, in the distal and dorsalquadrant thereof when being in the base position.

According to one embodiment, at least one extending portion extendscircumferentially along said equator line, in the distal, dorsal andproximal quadrant thereof when being in the base position.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said second portioncircumferentially extends along at least ¼ of said circular equatorline.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said second portioncircumferentially extends along at least ⅓ of said circular equatorline.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said second portioncircumferentially extends along at least ½ of said circular equatorline.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portion circumferentiallyextends along at least ¼ of said circular equator line.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portion circumferentiallyextends along at least ⅓ of said circular equator line.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portion circumferentiallyextends along at least ½ of said circular equator line.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portion circumferentiallyextends along at least 1/10 of said circular equator line.

According to one embodiment, at least a first portion of said medicaldevice is an extending portion, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portion circumferentiallyextends along at least 1/10 of said circular equator line, and saidsecond portion circumferentially extends along at least ¼ of saidcircular equator line.

According to one embodiment, at least two first portions of said medicaldevice are extending portions, extending beyond said circular equatorline, and at least a second portion is a portion not extending beyondsaid circular equator line, wherein said first portions eachcircumferentially extends along at least 1/10 of said circular equatorline, and said second portion circumferentially extends along at least ¼of said circular equator line.

According to one embodiment, at least two first portions of said medicaldevice are extending portions, extending beyond said circular equatorline, and wherein one of said extending portions extends further thanthe other extending portion.

According to one embodiment, said medical device further comprises twosecond portions not extending beyond said circular equator line, andwherein said two first extending portion circumferentially extends alongsaid equator line between said two second portions.

According to one embodiment, said medical device further comprises atleast one hole, and wherein said at least one hole is adapted to receivea fixating member, for fixating said medical device to the femoral bone.

According to one embodiment, said hole is adapted to receive a screw forfixating said medical device to the femoral bone.

According to one embodiment, said medical device comprises at least oneextending portion adapted to clasp the caput femur, or a prostheticcaput femur, for restraining said caput femur, or prosthetic caput femurin said medical device, and wherein said medical device is adapted torelease the caput femur or prosthetic caput femur from said medicaldevice when a predetermined strain is placed on said medical device.

According to one embodiment, said extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat adduction is restricted more degrees than flexion.

According to one embodiment, said extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat abduction is restricted more degrees than flexion.

According to one embodiment, said extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat adduction is restricted more degrees than extension.

According to one embodiment, said extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat abduction is restricted more degrees than extension.

The medical device could further comprise a prosthetic replacement forthe caput femur, adapted to be received in the bowl shaped innersurface, wherein said prosthetic replacement for the caput femurreplacement comprises a spherical portion and an elongated member,adapted to be fixated to the pelvic bone by the elongated member beingfixated to said spherical portion of said prosthetic replacement for thecaput femur, wherein:

a) said inner surface comprises an equator line, being the largestcircular circumference of said inner contacting surface, being a surfaceadapted to be in contact with said caput femur, or prostheticreplacement therefore, and

b) said at least one extending portion passes beyond said equator line,such that the end portion of said contacting portion of said innersurface forms a circular extension line having a smaller circumferencethan said equator line, and

c) said at least one extending portion circumferentially extendsdiscontinuously along said equator line, such that a portion of saidelongated member can be placed between said extension line and saidequator line, when said medical device being implanted.

The medical device could comprises a prosthetic replacement for thecaput femur having a spherical portion, comprising a spherical portionand an elongated member, adapted to be fixated to the pelvic bone by aconnection via the elongated member fixated to said spherical portion ofsaid prosthetic caput femur, wherein

a) an inner surface comprises an equator line, being the largestcircular circumference of said inner surface,

b) at least one extending portion passes beyond said equator line, suchthat the end portion of said contacting portion of said inner surfaceforms a circular extension line having a smaller circumference than saidequator line, and

c) said at least one extending portion circumferentially extendsdiscontinuously along said equator line, such that a portion of saidelongated member can be placed between said extension line and saidequator line, when said medical device being implanted.

The medical device could have at least one of extending portion, whenimplanted, is adapted to be placed such as to restrict the motion rangeof the hip joint, and wherein said extending portion is adapted to beplaced or shaped such that at least one of adduction, abduction,flexion, extension, a combination of flexion and adduction or abduction,a combination of extension and adduction or abduction, rotation in,rotation out, and any combination of rotation in or out and the otherdescribed movements, is restricted more degrees from maximal movementthan any of the other.

The at least one extending portion could allow different movementrestrictions in different movement directions, wherein said extendingportion is constructed according to at least one of the followingalternatives; a) circumferentially extending s discontinuously alongsaid equator line having with enough circumferential distance lackingany extending portion and b) extendings with different distal extensionin different extending portions or part of such portions of saidcircumferential extension, in either a orb allowing for differentmovement restrictions in different movement directions.

The medical device could, comprising a locking member for in situlocking the medical device, wherein: said locking member is adapted tolock said a prosthetic replacement for the caput femur fixated to thepelvic bone, such that the caput femur or prosthetic caput femur remainsclasped and restrained in said inner surface, and said locking member isadapted to lock said at least one extension portion, when implanted,having at least the end portion of the extension portion radially fixedwithin said circular extension line.

The locking member is adapted to lock in at least a first and secondlocking position.

The locking member is adapted to lock in at least a first and a secondlocking position, and wherein said locking member is adapted to; in saidfirst locking position, lock a first size caput and/or collum femur, andin said second locking position, lock a second smaller size caput femurand/or collum femur.

A method using a medical device according to any of the precedingmedical device claims is further provided, for implantation in a hipjoint of a patient, comprising the steps of;

fixating said medical device to the femoral bone of the patient, andwherein said medical device comprises an inner and an outer surface,wherein a contacting portion of said inner surface is bowl shaped andspherical and adapted to face the center of the hip joint,

placing the inner bowl shaped surface facing proximally towards thecenter of the hip joint, and

fixating a prosthetic replacement for the caput femur fixated to thepelvic bone having a ball shaped spherical portion

receiving said prosthetic replacement for the caput femur inside saidinner bowl shaped surface, wherein said medical device comprises atleast one extending portion, extending said contacting portion of saidinner surface such that said at least one extending portion clasps saidspherical portion,

clasping said prosthetic replacement for the caput femur, such that saidspherical portion is restrained in said bowl shaped inner surface ofsaid medical device.

The inner surface comprises an equator line, being the largest circularcircumference of said inner contacting surface, being a surface adaptedto be in contact with said caput femur replacement, and

said at least one extending portion passes beyond said equator line,such that the end portion of said contacting portion of said innersurface forms a circular extension line having a smaller circumferencethan said equator line, and

said at least one extending portion circumferentially extendsdiscontinuously along said equator line, such that a portion of saidelongated member can be placed between said extension line and saidequator line, when said medical device being implanted together with theprosthetic replacement for the caput femur, wherein the methodcomprising the steps of;

wherein the step of placing the inner surface involves the step ofplacing an inner surface comprising at least one extending portion

moving said femoral bone to place said elongated member between saidextension line and said equator line.

The method could further comprises the steps of cutting the skin in thehip region dissecting the hip joint implanting the medical device in ahip joint of a patient, fixating a ball shaped replacement of caputfemur on the opposite side therefore to the pelvic bone of the patient,fixating a bowl shaped acetabulum replacement on the opposite side andtherefore to the femoral bone of the patient, wherein said acetabulumreplacement comprises an inner and an outer surface, having a contactingportion of said inner surface being spherical and bowl shaped facing theinner surface to the center of the hip joint having at least oneextending portion, extending a contacting portion for contacting thecaput femur replacement, placing a caput femur replacement, such thatsaid extending contacting portion of said inner surface is clasping saidspherical portion of said caput femur replacement, such that said caputfemur replacement is restrained in said bowl shaped inner surface.

The inner surface comprising an equator line being the largest circularcircumference of said inner contacting surface, wherein said at leastone extending portion is

passing beyond said equator line, such that the end portion of saidcontacting portion of said inner surface forms a circular extension linehaving a parallel smaller circumference than said equator line, the endportion being the most distal portion of the inner surface being incontact with said caput femur or artificial replacement therefore,

placing said said caput femur or artificial replacement thereforesymmetrically in said inner surface, and wherein said at least oneextending portion is

extending circumferentially discontinuously along said equator line,wherein said caput femur replacement is extending into en elongatedmember, the method involves,

placing a portion of said elongated member between said extension lineand said equator line when moving said caput femur or artificialreplacement therefore in relation to said inner surface.

The at least one extending portion is mounted according to at least oneof the following alternatives:

a) extending circumferentially discontinuously along said equator linehaving enough circumferential distance lacking any extending portion andb) extending with different distal extension in different extendingportions or part of such portion of said circumferential extension.

The method could comprise the following steps:

a) cutting the skin in the hip region

b) dissecting the hip joint

c) implanting the medical device in a hip joint of a patient,

d) fixating the artificial replacement of an acetabulum to the femoralbone of the patient, comprising an inner and an outer surface, having acontacting portion of said inner surface being spherical and bowl shaped

e) facing the inner surface to the center of the hip joint having atleast one extending portion, extending a contacting portion forcontacting the caput femur or a prosthetic replacement therefore,

f) placing a caput femur or an artificial replacement therefore to thepelvic bone having a spherical portion, such that said extendingcontacting portion of said inner surface is

g) clasping said spherical portion of said caput femur, or an artificialreplacement therefore,

h) placing said locking member such that said caput femur, or artificialreplacement therefore is restrained in said bowl shaped inner surface,and

i) locking said caput femur or artificial caput femur in said claspedand restrained position in said inner surface, by

j) fixating radially at least the end portion of the at least oneextension portion within said circular extension line.

Please note that any embodiment or part of embodiment, feature, method,associated system, part of system described herein or in the associatedfigures may be combined in any way.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to theaccompanying drawings, in which

FIG. 1a shows pelvis in a frontal view,

FIG. 1b shows pelvis in a frontal view,

FIG. 1c shows the hip joint in section,

FIG. 2a shows pelvis in a lateral view,

FIG. 2b shows pelvis in a lateral view,

FIG. 2c shows pelvis in a perspective view from below,

FIG. 2d shows pelvis in a perspective view from below,

FIG. 2e shows the acetabulum, schematically,

FIG. 2f shows the acetabulum, schematically,

FIG. 2g shows pelvis in a perspective view from below,

FIG. 3 shows pelvis in a lateral view,

FIG. 4 shows a prosthetic replacement for the acetabulum, according toone embodiment,

FIG. 5 shows the hip joint in section, when a prosthetic replacement forthe acetabulum, and a medical device has been implanted,

FIG. 6a shows the pelvic region in a frontal view,

FIG. 6b shows the pelvic region in a frontal view,

FIG. 7 shows the pelvic region in a frontal view,

FIG. 8 shows a medical device placed in the femoral bone,

FIG. 9 shows the femoral bone in a lateral view,

FIG. 10 shows the femoral bone in a lateral view,

FIG. 11 shows the femoral bone in a lateral view,

FIG. 12 shows the femoral bone in a lateral view,

FIG. 13 shows the femoral bone in a lateral view,

FIG. 14 shows a medical device placed in the femoral bone,

FIG. 15a-15f shows embodiments of prosthetic replacements for theacetabulum,

FIG. 16a shows an embodiment of the locking/releasing member,

FIG. 16b shows the hip joint in section in an embodiment when thelocking/releasing member locks an artificial caput femur in artificialacetabulum.

FIG. 16c shows the hip joint in section in an embodiment when thelocking/releasing member releases the artificial caput femur from theartificial acetabulum.

FIG. 16d shows another embodiment of the locking/releasing member,

FIG. 16e shows the hip joint in section in an embodiment when thelocking/releasing member according to the embodiment of FIG. 36d locksthe artificial caput femur to the artificial acetabulum.

FIG. 16f shows the hip joint in section in an embodiment when thelocking/releasing member according to the embodiment of FIG. 36dreleases the artificial caput femur from the artificial acetabulum.

FIG. 16g shows another embodiment of the locking/releasing member,

FIG. 16h shows another embodiment of the locking/releasing member,

FIG. 16i shows the hip joint in section when an artificial hip joint isbeing assembled,

FIG. 16j shows the hip joint in section when an artificial hip joint isbeing assembled,

FIGS. 16k and 16l shows the hip joint in section when an artificial hipjoint is assembled,

FIGS. 16m and 16n shows the hip joint in section according to theembodiment of FIG. 16k , when released.)

DETAILED DESCRIPTION

The hip joint is a synovial ball and socket joint which permits a largemotion range for allowing a plurality of different movements of thelower limb. From a neutral position the following movements of the hipjoint are normally possible: Lateral or external rotation, 30° with thehip extended, 50° with the hip flexed, medial or internal rotation 40°,extension or retroversion 20°, flexion or anteversion 140°, abduction50° with hip extended, 80° with hip flexed, adduction 30° with hipextended, 20° with hip flexed.

When replacing the natural hip joint with a prosthetic hip joint, thedepth of the prosthetic acetabulum will affect the motion range, thedeeper the acetabulum bowl is made the more restrictive it is to themotion range. A deeper bowl has the advantage of reducing the risk ofhip joint luxation, the risk of which is a major drawback withprosthetic hips of today.

The anatomy of the hip joint and its surroundings is further disclosedin: Marieb et al., Human Anatomy, 2003, Benjamin Cummings, San Rancisco,pages 195-202 and in Moore et al., Clinically oriented anatomy, 1999,Lippincott; Williams &Wilkins, Baltimore, pages 501-653, both herebyincorporated by reference.

Centrally in the body should herein be understood as a point ofreference located at the intersection of the Median plane and theCoronal plane and in the center part of the heart along a longitudinalaxis (Caudal-Cranial). Proximal and distal are direction or locationterms used in relation to said point centrally in the body and hence adistal point is a point farther away from the central point in relationa proximal point of the same structure. Any plane disclosed herein is tobe understood as having infinite extension. Other anatomical terms usedherein are further described in Moore et al., Clinically orientedanatomy, 1999, Lippincott, Williams & Wilkins, Baltimore, pages 2-10,which is hereby incorporated by reference.

Functional hip movements are to be understood as movements of the hipthat at least partly correspond to the natural movements of the hip. Onsome occasions the natural movements of the hip joint might be somewhatlimited or altered after hip joint surgery, which makes the functionalhip movements of a hip joint with prosthetic surfaces somewhat differentthan the functional hip movements of a natural hip joint.

Everyday activities is to be understood as activities which are notconnected to any extreme movements, such that some physical sportsrequire. For example, everyday activities comprise: walking, sitting,cycling etc.

The functional position of an implantable medical device or prosthesisis the position in which the hip joint can perform functional hipmovements. The final position is to be understood as a functionalposition in which the medical device needs no further position change tofunction.

Arthroscopy is to be understood as key hole surgery performed in ajoint, since the arthroscopic procedure could be performed in theabdomen of the patient some of the steps of this arthroscopic procedureis more laparoscopic, however for the purpose of this invention the twoterms arthroscopy and laparoscopy is used synonymously and for thepurpose of this invention the main purpose of these methods are is thatthey are minimally invasive.

Elastic deformation is when a material deforms under stress (e.g.external forces), but returns to its original shape when the stress isremoved. A more elastic material is to be understood as a materialhaving a lower modulus of elasticity. The elastic modulus of an objectis defined as the slope of its stress-strain curve in the elasticdeformation region. The elastic modulus is calculated as stress/strain,where stress is the force causing the deformation, divided by the areato which the force is applied; and strain is the ratio of the changecaused by the stress.

Elasticity is to be understood as a materials ability to deform in anelastic way.

Stiffness is to be understood as the resistance of an elastic body todeformation by an applied force.

Biocompatible material is to be understood as being a material with lowlevel of immune response. Biocompatible materials are sometimes alsoreferred to as biomaterials. Analogous is biocompatible metals abiocompatible metal with low immune response such as titanium ortantalum. The biocompatible metal could also be a biocompatible alloycomprising at least one biocompatible metal.

Form fitting is to be understood as an element having a part or sectionwhich is adapted to enable a mechanical connection of said element to atleast one other element using said part or section. Form fittedstructure is a structure of an element which enables form fitting.

In the following a detailed description of embodiments of the presentinvention will be given. In the drawing figures, like reference numeralsdesignate identical or corresponding elements throughout the severalfigures. It will be appreciated that these figures are for illustrationonly and are not in any way restricting the scope of the invention.Thus, any references to direction, such as “up” or “down”, are onlyreferring to the directions shown in the figures. Also, any dimensionsetc. shown in the figures are for illustration purposes.

FIG. 1a shows the pelvis in a frontal view. Pelvis comprises the rightand left hip bone making up the pelvic bone, in turn comprising theSacrum 1803, Ilium 1802, Pubis 1804 and Ischium 1801. The hip jointhouses the right and left acetabulum 8 a,b placed laterally and distallyin the pelvis. The acetabulum 8 a,b being a spherically shaped cavity inthe hip bones making up one of the parts of the hip joint, theacetabulum 8 a,b being adapted to house the caput femur 5, being theproximal portion of the femoral bone 7 having a spherical contactingsurface adapted to be placed in the acetabulum 8 a,b and thus creatingthe operable hip joint. The pelvis has a right-left axis X extendingsubstantially from the bottom of the left acetabulum 8 a to the bottomof the right acetabulum 8 b, the pelvis further having a caudal-cranialaxis Y extending perpendicular to said right-left axis, centrally andsubstantially along the length of the patient, passing the dorsalportions of the pubic symphysis 1805 and substantially following thespinal cord 1806, intersecting the left-right axis X

FIG. 1b shows the pelvis in a frontal view disclosing a second,displaced coordinate system. The second displaced coordinate system hasits origin O′ in the bottom of the acetabulum bowl 8 a. The axis X and Yhave, in a frontal view, been rotated the angle β, creating the axis X′and Y′. In the defined base position, the acetabulum center axis X′ isaligned with the caput and collum femur center axis CX, the caput andcollum femur center axis CX is an axis in the extension of the collumand caput femur axis, in the center thereof. The hip joint substantiallybeing in it base position when the patient is standing up or lying down.In said base position, the acetabulum center axis X′ goes through apoint O′ being the origin O′ in the bottom of the acetabulum bowl 8 a,and a center point CP, being a point in the center of a circle definedby the edges of the acetabulum bowl 8 a, and further trough the top ofthe caput femur 5 and following inside of the collum femur 6, alignedwith the collum femur 6. The axis Y′ is perpendicular to the axis X′ andgoes through the origin O′ in the bottom of the acetabulum bowl 8 a,parallel to a plane defined by the circle defined by the edges of theacetabulum bowl 8 a.

FIG. 1c shows the right pelvic bone 9 in section disclosing the second,displaced coordinate system. The origin O′ is in the bottom of theacetabulum bowl 8. The axis X′ is aligned with the caput 5 and collum 6femur center axis CX, when the hip joint is in it base position when thepatient is standing up or lying down with extended leg. In said baseposition the axis X′ is goes through a point O′ being the bottom of theacetabulum bowl 8, and a center point CP, being a point in the center ofa circle defined by the edges of the acetabulum bowl 8, and furthertrough the top of the caput femur 5′ and following inside of the collumfemur 6, aligned with the collum femur 6. The axis Y′ is perpendicularto the axis X′, goes through the origin O′ in the bottom of theacetabulum bowl 8, parallel to the plane PC defined by the circledefined by the edges of the acetabulum bowl 8.

FIG. 2a shows the pelvis in a lateral view, thus displaying theposterior side of Ilium 1802, the anterior side of Ichum 1801, theanterior side of Pubis 1804, and Sacrum 1803 in a lateral view. Thepelvis has furthermore a dorsoventral axis Z being perpendicular to thecaudal-cranial axis Y and the right-left axis X shown in FIG. 1, andintersecting them both creating a common origin O for the three axisX,Y,Z. The dorsoventral axis Z and the caudal-cranial axis Y thus beingoriented such that a horizontal pelvis plane PXZ extends from thedorsoventral axis Z, and a coronal plane PXY extends from thecaudal-cranial axis Y.

FIG. 2b shows the pelvis in a plane view from the side and slightly frombelow, in the direction of the axis X′ (further disclosed with referenceto FIGS. 1b and 1c ). The view of FIG. 2b displaying the axis Y′ and Z′with origin O′ in the bottom of the acetabulum bowl 8 making up theacetabulum coordinate system. The axis Y′, Z′, in this plane view,dividing the acetabulum bowl 8 into four quadrants: the proximal-frontalquadrant 1807, the distal-frontal quadrant 1808, the distal-dorsalquadrant 1809 and the proximal-dorsal quadrant 1810.

FIG. 2c shows the pelvis M a perspective view from below and slightlyfrom the front, displaying the right-left axis X passing through thecenter of the right and left acetabulum 8. The right-left axis X isperpendicular to the dorsoventral axis Z which also is perpendicular tothe caudal-cranial axis Y. The coronal plane PXY extends from thedorsoventral axis Y, and the horizontal pelvis plane PXZ extends fromthe dorsoventral axis Z, thus being perpendicular to the coronal planePXY.

FIG. 2d shows the coordinate system X,Y,Z and planes PXY, PXZ of FIG. 2c, and the second, displaced, coordinate system X′, Y′, Z′ being thecoordinate system of the acetabulum 8, also shown in FIG. 2b . The axisof the coordinate system of the acetabulum X′, Y′, Z′ having theirorigin O′ in the bottom of the acetabulum bowl 8, the axis X′ beingaligned with the caput and collum center axis. FIG. 2d further disclosesthe vertical acetabulum plane PX′Y′ and the horizontal acetabulum planePX′Z′, PX′Y′ being defined by the axis X′,Y′ and the vertical acetabulumplane PX′Z′ being defined by the axis X′,Z′. The planes PX′Y′ and PX′Z′dividing the acetabulum bowl 8 into four quadrant, the proximal-frontalquadrant 1807, the distal-frontal quadrant 1808, the distal-dorsalquadrant 1809 and the proximal-dorsal quadrant 1810, in accordance withwhat is previously disclosed, with reference to FIG. 2b . FIG. 2dfurther shows the location of foramen obturatum 1871.

FIG. 2e shows, schematically how the acetabulum coordinate systemX′,Y′,Z′ relates to the hemisphere defined by the acetabulum bowl 8.

FIG. 2f shows, schematically, how the vertical acetabulum plane PX′Y′,and the horizontal acetabulum plane PX′Z′ divides the acetabulum 8 intofour quadrant; the proximal-frontal quadrant 1807, the distal-frontalquadrant 1808, the distal-dorsal quadrant 1809 and the proximal-dorsalquadrant 1810, in accordance with the previously disclosed, withreference to FIGS. 2b and 2 d.

FIG. 2g shows the view of FIG. 2d , and in addition it shows thehorizontal and vertical acetabulum planes PX′Y′ and PX′Z′ also being thecaput and collum femur horizontal and vertical planes PX′Y′ and PX′Z′,analogically dividing the caput and collum femur into four quadrants.

FIG. 3 shows pelvis in the same view as FIG. 2b . Here the vertical andhorizontal acetabulum planes PX′Y′ and PX′Z′ (further disclosed withreference to FIG. 2d ) are shown in a strict plane view. Two furtherplanes PX″Y″ is introduced in FIG. 3, which planes are rotated an angleα of 45° clockwise. The planes PX″Y″ and PX″Z″, analogous to the planesPX′Y′ and PX′Z′, divides the acetabulum bowl into four differentquadrant, being a proximal quadrant 1811, a frontal quadrant 1812, adistal quadrant 1813 and a dorsal quadrant 1814.

FIG. 4 shows a medical device for implantation in a hip joint of apatient. The medical device is adapted to be fixated to the femoral boneof the patient in an opposite embodiment, for example by means of anadhesive, such as bone cement, or mechanical fixating members, such asorthopedic screws. The medical device comprises an inner 1827 and anouter 1828 surface. A contacting portion of the inner surface 1827 isspherical and faces the center of the hip joint, when the medical deviceis implanted. The inside of the medical device is adapted to receive aprosthetic replacement for a caput femur adapted to be fixated to thepelvic bone having a spherical portion, and the spherical contactingportion of the inner surface 1827 is adapted to be in contact with aspherical portion of the outer surface of the prosthetic replacement ofthe caput femur. The medical device, comprises two extending portions1823 a,b, extending the contacting portion of the inner surface 1827′such that the extending portions 1823 a,b clasps the spherical portionof a prosthetic replacement of a caput femur, for restraining thespherical portion in the medical device. The medical device is adaptedto receive the prosthetic spherical portion, fixated to the pelvic bone,connected via a prosthetic elongated portion. The inner surface 1827comprises an equator line 1821, being the largest circular circumferenceof the inner surface. The two extending portions passes beyond theequator line 1821, such that an end portion 1829 of the contactingportion, here being of the extending portion 1823 b of the inner surface1827, forms a circular extension line 1822 placed proximal to theequator line 1821, when the medical device is implanted, and having asmaller circumference than the equator line 1821; thus a distance 1826between a center axis P of the medical device and the extension line1822 is shorter than a distance 1825 between the center axis P and theequator line 1821.

FIG. 5 shows the medical device described with reference to FIG. 4 whenimplanted. According to this embodiment the medical device is adapted tobe fixated using orthopedic screws 1830, mechanically fixating themedical device to the femoral bone 5, by the medical device comprisingholes through which the screws 1830 are placed. In FIG. 5 the contactingportion of the inner surface 1827 has been placed in contact with theprosthetic spherical portion being connected to a the prostheticelongated portion 2201, the prosthetic spherical 45 and elongatedportions 2201 replacing the proximal portion of the femoral bone. Thetwo extending portions 1823 a and 1823 b extending the contactingportion of the inner surface and clasping the spherical portion 45, forrestraining the spherical portion in the medical device. The innersurface comprising the equator line 1821, and the extending portions1823 a,b passing beyond the equator line 1821 and comprising the moreproximal extension line 1822 having a smaller circumference than theequator line 1821. The more proximal extension line 1822 being placed ata distance D1 from the equator line 1821. According to this embodimentthe extension line 1822 is parallel to the equator line 1821, howeverthis is not necessarily so in other embodiments. The extension portion1823 a according to the embodiment shown in FIG. 5 extendscircumferentially along the equator line, a distance D2. Along anotherportion of the equator line, a distance D3, there are no extendingportion, which enables the elongated portion 2201 to enter the spacebetween the first and second extending portions 1823 a,b which creates alarger movement range of the hip joint, for further increase of themovement range, the recess 2203 in the elongated portion 2201 is adaptedfor some section of the extending portion to enter the recess 2203.

The extending portion, according to any of the embodiments, adapted toclasp the prosthetic spherical portion, for restraining it theprosthetic acetabulum 65, could further be adapted to release theprosthetic spherical portion 45 when a large enough strain is placed onthe joint. This feature enables the prosthetic spherical portion to befixedly attached in the prosthetic acetabulum 65 in normal use, and bereleased from the prosthetic acetabulum, e.g. in case of an accident,thus reducing the risk of damaging the bodily structures, such as thefemoral bone, or the fixations between bodily structures and prostheticparts.

According to one embodiment, the extending elements are placed such thatthe extending elements restrict the motion range minimally, or in wayswhich are not limiting the motion range used in everyday life. This isenabled through the placing of the extending portions, or theinteraction between the extending portion and adaptations of theprosthetic elongated portion. The hip joint is a synovial ball andsocket joint which permit a large motion range for allowing a pluralityof different movements of the lower limb. From a neutral position, thefollowing movements of the hip joint are normally possible: lateral orexternal rotation, 30° with the hip extended, 50° with the hip flexed,medial or internal rotation 40°, extension or retroversion 20°, flexionor anteversion 140°, abduction 50° with hip extended, 80° with hipflexed, adduction 30° with hip extended, 20° with hip flexed. In themovement ranges of abduction and adduction the depth of the acetabulumbowl and thus the extending portions does not restrict the motion rangein a critical way since the motion range of the normal hip is restrictedin these movements, in normally agile persons, by the muscles, tenorsand ligaments surrounding the hip joint

FIG. 6a shows a frontal view of pubis and the proximal portions of thefemoral bones 7 when two embodiments prosthetic replacement for theacetabulum 65 has been implanted in the hip joint. The prostheticreplacements for the acetabulum shown comprises one extending portion1823, here placed dorsal to the vertical acetabulum plane PX′Y′ in thebase position, thus only partially limiting abduction in far excess of50°. According to the embodiment shown, the extending portion 1823extends circumferentially along the equator line 1821 about 1/10 of thelength of the equator line 1821, however in other embodiment theextending portion 1823 extends along as much as half of the length ofthe equator line 1821, and in other embodiments the extending portion1823 extends as lithe as about 1/30 of the length of the equator line1821. The prosthetic replacement for the acetabulum placed in the leftfemoral bone comprises two extending portions 1823 a,b, both beingplaced dorsal the corresponding vertical acetabulum plane PX′Y′ of theleft acetabulum (not shown) in the base position, thus limiting themotion range of the hip joint in a nonrestrictive way, in relation toeveryday activities. In both the right and left embodiment the extendingportions 1823 extends discontinuously along the equator line 1821 thusenabling the elongated portion 2201 to partially be placed between theequator line and the extension line, and in the left embodiment, beplaced between the extending portions 1823 a,b thus entering the cavitybetween the extending portions 1823 a,b. The recess 2203 of theprosthetic elongated portion 2201 implanted in the right hip joint isradially placed, in relation to the caput and collum center axis, suchthat the a section of the prosthetic elongated portion 2201, can enterthe recess for further increasing the movement range of the prostheticacetabulum surface 65 in relation to the elongated 2201 and spherical 45a portion. The curving of the prosthetic elongated portion 2201implanted in the left hip joint is radially placed, in relation to thecaput and collum center axis, for further increasing the movement rangeof the prosthetic acetabulum surface 65 in relation to the elongated2201 and spherical 45 b portion.

FIG. 6b shows a frontal view of pubis and the proximal portions of thefemoral bones 7, when two further embodiments of the prostheticreplacements have been implanted. The embodiment shown placed on theright side is an embodiment in which the prosthetic elongated portion2201 a comprises a first 2203 a and second 2203 b recess placed at therestricting portion of the elongated portion 2201 a. The prostheticelongated portion 2201 is connected to a prosthetic spherical portion 45a which is restrained in a prosthetic replacement for the acetabulum 65a fixated to the femoral bone. The prosthetic replacement for theacetabulum 65 a comprises extending portions 1823 clasping theprosthetic spherical portion 45 a and thus restraining the sphericalportion in the prosthetic replacement for the acetabulum 65 a. Theextending portions 1823 is placed in the proximal quadrant in the baseposition, thus limiting the motion range of the hip joint in a nonrestrictive way, in relation to everyday activities. According to theembodiment shown, the extending portion 1823 extends circumferentiallyalong the equator line 1821 about 1/10 of the length of the equator line1821, however in other embodiments the extending portion 1823 extendsalong as much as half of the length of the equator line 1821, and inother embodiment the extending portion 1823 extends as lithe as about1/30 of the length of the equator line 1821. The prosthetic elongatedportion 2201 b shown placed in the left hip joint comprises a narrowportion connected to the prosthetic spherical portion 45 b. The narrowportion enables a relatively large motion range in relation to theelongated portion even though the prosthetic replacement for theacetabulum comprises extending portions 1823 a,b extending beyond theequator line of the prosthetic spherical portion 45 b, thus clasping thespherical portion and restraining it in a fixated position.

FIG. 7 shows the pelvis and the proximal portions of the femoral bones 7including the embodiment of FIG. 25a , with the difference that thenatural caput femur has been replaced by a prosthetic replacement forthe acetabulum. The prosthetic elongated portion 2201 is herecoordinated with the extending portions 1823 of the prostheticreplacement for the acetabulum 65 a,b for further improving the motionrange of the hip joint, or not limiting the natural motion range of thehip joint.

FIG. 8 shows the medical device according to an embodiment in which themedical device comprises two extending portions 1823 a,b. The medicaldevice is placed on a prosthetic elongated portion 2201, to which aprosthetic spherical portion 45 is attached. The prosthetic elongatedmember 2201 is here adapted to further improve the motion range of thehip joint, or not limiting the natural motion range of the hip joint, bythe prosthetic elongated portion 2201 comprising a recess 2203 in whichthe extending portions 1823 can enter.

FIG. 9 shows the pelvis in a lateral view, the prosthetic replacementfor the acetabulum 65 in the femoral bone comprises two extendingportions 1823 a,b, both extending circumferentially along the equatorline (as disclosed in for example FIG. 5) dorsal to the caudal-cranialaxis Y when being in the base position and being adapted to clasp thecaput femur or a prosthetic replacement therefor. The extending portions1823 a,b extending dorsal to the caudal-cranial axis Y when being in thebase position and thus reducing the limiting effect that the extendingportions 1823 a,b, have on the motion range of the hip joint. Accordingto the embodiment shown in FIG. 9 the extending portion 1823 a, placedproximally in the acetabulum, extends circumferentially a distance ofabout ¼ of the length of the equator line, and the extending portion1823 b, placed distally in the acetabulum when being in the baseposition, extends circumferentially a distance of about 1/10 of thelength of the equator line, however it is equally conceivable that thisrelationship is the other way around, or that any of the extendingportions circumferentially extends a distance of as much as half of thelength of the equator line, thus extending the entire distance of theequator line being dorsal to the vertical acetabulum plane PX′Y′, orthat any of the extending portions 1823 a,b extends a distance being aslithe as 1/30 of the distance of the equator line. According to theembodiment shown in FIG. 9, the first extending portion 1823 a extendsin distal-lateral direction from the acetabulum, and the secondextending portion 1823 b extends medially towards foramen obturatum whenbeing in the base position.

FIG. 10 shows the pelvis in a lateral view, the prosthetic replacementfor the acetabulum 65 in the femoral bone comprises two extendingportions 1823 a,b, the two extending portions 1823 a,b extends in theproximal quadrant 1811 and the distal quadrant 1813 when being in thebase position, respectively.

There are multiple ways in which the extending portions 1823 can beadapted to reduce the effects that the extensions have on the motionrange of the hip joint.

FIG. 11 shows the pelvis in a lateral view, the prosthetic replacementfor the acetabulum 65 in the femoral bone shown comprises one extendingportion 1823 extending and being adapted to clasp the caput femur, or aprosthetic replacement therefor. The extending portion 1823 extendscircumferentially along the equator line within the proximal quadrant1811 when being in the base position, which is further disclosed withreference to FIG. 3. According to the embodiment shown in FIG. 4, theextending portion 1823 extends in distal-lateral direction from theacetabulum when being in the base position.

FIG. 12 shows the pelvis in a lateral view, the prosthetic replacementfor the acetabulum 65 in the femoral bone shown comprises a continuouslyextending portion 1823 with two extending portions 1823 a and 1823 bextending further in relation to the average extension of the extendingportion. The entire extending portion is placed in the proximal, distaland dorsal quadrants and the extending portions 1823 a,b extendingfurther than the average extension of the extending portion 1823 extendsin the proximal and distal quadrant when being in the base position.

FIG. 13 shows the pelvis in a lateral view, the prosthetic replacementfor the acetabulum 65 in the femoral bone shown comprises four extendingportions 1823 a,b,c,d, wherein the first 1823 a and second 1823 bextending portions extends in the proximal and distal quadrant,respectively, thus the first extending portion 1823 a extending indistal-lateral direction from the acetabulum, and the second extendingportion 1823 b extending medially towards foramen obturatum when beingin the base position. The third extending portion 1823 c when being inthe base position extending in the frontal quadrant 1812, out from theacetabulum in dorsal direction, extends less than the first and secondextending portion, since extending portions 1823 c in the frontalquadrant is more limiting to the normal motion range of the hip joint.The fourth extending portion 1823 d extends in the dorsal quadrant inaccordance with the third extending portion 1823 c do not extend as faras the first and second extending portions when being in the baseposition.

FIG. 14 shows an alternative embodiment of the prosthetic replacementfor the acetabulum 65. In the alternative embodiment, the prostheticreplacement for the acetabulum 65 comprises a first part 1841 adapted tobe fixated to the femoral bone of the patient. The first part comprisesan inner contacting surface adapted to be in movable connection with anouter contacting surface of a second part 1842. The second part 1842 isrotatably fixated to the first part 1841 by a rotatable connectingmember 1843. An outer contacting surface of a prosthetic sphericalportion 45 is adapted to be placed in contact with the inner surface ofthe second part 1842 and be movable in multiple directions, thusreplicating the natural ball and socket joint of the hip. The secondpart 1842 comprises two extending portions 1823 a,b extending beyond theequator line 1845 of the second part 1842. The extending portions 1823a,b extends longitudinally discontinuously along the equator line, thuscreating an area between the extending portions, in which area a portionof the prosthetic elongated portion can be placed, thus being placedpartially between the equator line 1845 and the extension line 1846. Theconstruction shown in FIG. 26 enables the second part 1842 to rotate ifthe prosthetic elongated portion 2201 engages the extending portions1823 a,b, which are sloped for this purpose. This way the second part1842 are always placed such that the prosthetic elongated portion 2201can be placed partially between equator line 1845 and the extension line1846, which creates an optimal range of movement whilst the second partclasps the prosthetic spherical portion 45, and thus restricting thespherical portion 45 in the second part 1842 of the prostheticreplacement for the acetabulum 65.

FIG. 15a shows the prosthetic replacement for the acetabulum 65according to one embodiment. In this embodiment the prostheticreplacement for the acetabulum 65 comprises two extending portions 1823a, b. The prosthetic replacement for the acetabulum 65 is according tothis embodiment adapted to be fixated to the femoral bone by means of anadhesive which is adapted to be placed in connection with the adhesiverecesses 1870 of the outer surface of the prosthetic replacement for theacetabulum 65.

FIG. 15b shows a prosthetic replacement for the acetabulum 65 similar tothe prosthetic replacement for the acetabulum 65 disclosed withreference to FIG. 15a , but with the difference that it comprises threeequally extending portions 1823 a,b,c.

FIG. 15c shows a prosthetic replacement for the acetabulum 65, similarto the prosthetic replacement for the acetabulum 65 disclosed withreference to FIG. 15a , but with the difference that it comprises twoequally extending portions 1823 a,b and one less extending portion 1823c.

FIG. 15d shows a prosthetic replacement for the acetabulum 65 similar tothe prosthetic replacement for the acetabulum 65 disclosed withreference to FIG. 15a , but with the difference that it comprises fourequally extending portions 1823 a,b,c,d.

FIG. 15e shows a prosthetic replacement for the acetabulum 65 similar tothe prosthetic replacement for the acetabulum 65 disclosed withreference to FIG. 15a , but with the difference that the two extendingportions are placed further from each other, and thus being adapted tobe placed in the proximal and distal quadrant, when implanted and beingin the base position.

FIG. 15f shows a prosthetic replacement for the acetabulum 65 similar tothe prosthetic replacement for the acetabulum 65 disclosed withreference to FIG. 15a , but further comprising a less extending portion1823 c placed between the first and second extending portions 1823 a,b.

The extending portions of the prosthetic replacement for the acetabulum65 which have been described could be made from an elastic material,enabling the extending portions to pass onto the a prosthetic sphericalportion, according to any of the embodiments herein.

FIG. 16a shows an embodiment of a locking/releasing member 116, whereinthe locking/releasing member 116 comprises a surface 1353 adapted to bein contact with the artificial convex hip joint surface (replacement forthe caput femur) (112 in FIG. 16b ), being a first piece, and slideagainst the hip joint surface, the locking member 116 is adapted to, ina first state, lock the artificial caput femur 112 to the artificialacetabulum surface (1340 in FIG. 16b ), and in a second state, releasesaid artificial caput femur 112 from said artificial acetabulum 1340.The locking/releasing member 116 is adapted to change from the first tothe second state when a predetermined amount of strain is placed on thelocking/releasing member 116. The locking/releasing member 116 comprisesfour holding members, here being elastic portions 1351, and thelocking/releasing member 116 is adapted to change from the first to thesecond state using the elasticity of the elastic portions 1351. Thelocking member 116 is adapted to be fixated to the femoral bone 7 usingscrews adapted to be placed in holes 1352 adapted therefor. According toanother embodiment (not shown) the holding members 1351 comprises atleast one holding member adapted to roll against the first piece, beingthe artificial convex hip joint surface 112.

FIG. 16b shows the hip joint in section when the two statelocking/releasing member 116 locks the artificial caput femur 112 in theartificial acetabulum 1340. The two state locking/releasing member 116is fixated to the femoral bone 7 using screws 121, and is here shown init first state in which the locking/releasing member 116 locks theartificial caput femur 112 to the artificial acetabulum 1340.

FIG. 16c shows the hip joint in section according to the embodiment ofFIG. 16b , but when the two state locking/releasing member 116 is in itsecond state, in which the locking/releasing member 116 releases theartificial caput femur 112 from the artificial acetabulum surface 1340.The construction with the locking/releasing member 116 reduces the riskof strain placed on the artificial joint injuring the fixation point,i.e. the contact with bone; it further enables the artificial joint tobe non-invasively relocated in case of luxation.

FIG. 16d shows an alternative embodiment of the two-statelocking/releasing member 116, in which the two-state locking/releasingmember 116 further comprises an elastic band 1361 adapted to encirclethe artificial caput femur 112, when implanted. The elastic band 1361could be an elastic polymer band, such as a polyurethane or siliconeband.

FIG. 16e shows a hip joint in section when the two-statelocking/releasing member 116 has been implanted, and being in its firststate. The two-state locking/releasing member 116 is fixated to thefemoral bone 7 using screws 121.

FIG. 16f shows the implantable device comprising the two-statelocking/releasing member 116 when in its second state, i.e. in the statein which the locking/releasing member 116 is adapted to release theartificial caput femur 112 through the elastic band 1361 encircling theartificial caput femur 112 is stretched so that the artificial caputfemur 112 can exit from the artificial acetabulum 1340. The constructionwith the locking/releasing member 116 reduces the risk of strain placedon the artificial joint injuring the fixation points, i.e. the contactwith bone; it further enables the artificial joint to be non-invasivelyrelocated in case of luxation.

The locking/releasing member 116 described with reference to FIGS.16a-16f are depicted in embodiments with a large hole in the pelvic bone9 occupied by a prosthetic part 118, however, it is equally conceivablethat the two state locking/releasing member 116 is used in embodimentswith a small hole in the pelvic bone 9, for a less invasive procedure,it is furthermore conceivable that the all of the embodiments disclosedof the medical device could be installed during conventional open hipjoint surgical procedure, penetrating the hip joint capsule. In thiscase the two state locking/releasing member 116 could be a part of afull prosthesis.

FIG. 16g shows an embodiment of a locking/releasing member 116, whereinthe locking/releasing member 116 comprises a spring 1371 creating theelasticity needed to change from a first state to a second state forreleasing the artificial caput femur 112 from the artificial acetabulum1340. The locking/releasing member 116 is adapted to change from thefirst to the second state when a predetermined amount of strain isplaced on the locking/releasing member 116. According to the embodimentshown in FIG. 16g the medical device further comprises a calibrationscrew 1372 placed in connection with the spring 1371 for calibrating theelasticity and thereby the amount of strain required for thelocking/releasing member to change from the first to the second state.

FIG. 16h shows an embodiment of the locking/releasing member in whichthe locking/releasing member comprises four rupture pins 1373 adapted tofail at a pre-determined strain, for allowing the locking/releasing 116members to change from the first to the second state. The pins are,according to this embodiment, made from a brittle material which couldbe adapted for the particular patient. In other embodiments (not shown)the rupture pins 1373 could be replaced by a rupture band, similar tothe elastic band, but adapted to fail at a pre-determined strain, or arupture band placed centrally.

FIG. 16i shows the hip joint in section when an artificial caput femur1375 a,b comprising two parts 1375 a and 1375 b is adapted to beinterconnected to form an interconnected artificial caput femur. Each ofthe two artificial part 1375 a, 1375 b, furthermore comprises a fixatingportion 1374 a, 1374 b adapted to be fixated to the inside of theacetabulum 8. The artificial caput femur is, after the interconnection,adapted to be placed in an artificial concave acetabulum 1340 placed inthe proximal portion of the femoral bone 7, for creating a functionalhip joint in an opposite embodiment.

FIG. 16j shows the hip joint in section when the interconnectedartificial caput femur 1375 has been placed in the acetabulum 8, andbeen fixated using the fixating portion 1374. The locking/releasingmember 116 has been placed onto the artificial caput femur 1375 usingthe spring 1371 creating the elasticity required to enable theartificial caput femur 1375 to be placed such that the locking/releasingmembers clasps the artificial caput femur 1375.

FIG. 16k shows the hip joint in section when the two statelocking/releasing member 116 locks the interconnected artificial caputfemur 1375 in the artificial acetabulum 1340. The two statelocking/releasing member 116 is fixated to the femoral bone 7 usingscrews 121, and is here shown in its first state in which thelocking/releasing member 116 locks the artificial caput femur 112 to theartificial acetabulum 1340.

FIGS. 16m and 16 n shows the hip joint in section according to theembodiment of FIG. 16k , but when the two state locking/releasing member116 is in its second state, in which the locking/releasing member 116releases the artificial caput femur 112 from the artificial acetabulumsurface 1340, by means of the spring 1371 creating the requiredelasticity. The construction with the locking/releasing member 116reduces the risk of strain placed on the artificial joint injuring thefixation point, i.e. the contact with bone; it further enables theartificial joint to be non-invasively relocated in case of luxation.

Please note that any embodiment or part of embodiment as well as anymethod or part of method could be combined in any way. All examplesherein should be seen as part of the general description and thereforepossible to combine in any way in general terms.

The medical device according to any of the embodiments could comprise atleast one material selected from a group consisting of:polybtrafluoroethylene (PTFE), perfluoroalkoxy (PFA) and fluorinatedethylene propylene (FEP). It is furthermore conceivable that thematerial comprises a metal alloy, such as cobalt-chromium-molybdenum ortitanium or stainless steel, or polyethylene, such as cross-linkedpolyethylene or gas sterilized polyethylene. The use of ceramic materialis also conceivable, in the contacting surfaces or the entire medicaldevice such as zirconium or zirconium dioxide ceramics or aluminaceramics. The part of the medical device in contact with human bone forfixation of the medical device to human bone could comprise a poorhousestructure which could be a porous micro or nano-structure adapted topromote the growth-in of human bone in the medical device for fixatingthe medical device. The porous structure could be achieved by applying ahydroxy-apatite (HA) coating, or a rough open-pored titanium coating,which could be produced by air plasma spraying, a combination comprisinga rough open-pored titanium coating and a HA top layer is alsoconceivable. The contacting parts could be made of a self lubricatedmaterial such as a waxy polymer, such as PTFE, PFA, FEP, PE and UHMWPEor a powder metallurgy material which could be infused with a lubricant,which preferably is a biocompatible lubricant such as a Hyaluronic acidderivate. It is also conceivable that the material of contacting partsor surfaces of the medical device herein is adapted to be constantly orintermittently lubricated. According to some embodiments the parts orportions of the medical device could comprise a combination of metalmaterials and/or carbon fibers and/or boron, a combination of metal andplastic materials, a combination of metal and carbon based material, acombination of carbon and plastic based material, a combination offlexible and stiff materials, a combination of elastic and less elasticmaterials, Corian or acrylic polymers.

Please note that any embodiment or part of embodiment as well as anymethod or part of method could be combined in any way. All examplesherein should be seen as part of the general description and thereforepossible to combine in any way in general terms.

The invention claimed is:
 1. A medical device for implantation in a hipjoint of a patient, said medical device comprises: a. an artificialacetabulum having an inner and an outer surface, wherein a contactingportion of said inner surface is bowl shaped and spherical and adaptedto face a natural acetabulum of a pelvic bone of the patient when saidmedical device is implanted, b. a prosthetic replacement for a caputfemur adapted to be fixated to a pelvic bone, said prostheticreplacement for the caput femur having a spherical portion adapted to beplaced in contact with the inner surface of the artificial acetabulum,and c. an elongated member comprising an acetabulum fixating surface,wherein the elongated member extends between the prosthetic replacementfor the caput femur and the acetabulum fixating surface, the acetabulumfixating surface is adapted to be placed in contact with the naturalacetabulum to fixate the prosthetic replacement for the caput femur tothe pelvic bone, wherein said artificial acetabulum comprises at leastone extending portion, extending said contacting portion of said innersurface such that said at least one extending portion is adapted toclasp said spherical portion of said prosthetic replacement for thecaput femur, such that said spherical portion is adapted to berestrained in said artificial acetabulum.
 2. The medical deviceaccording to claim 1, wherein: a) said inner surface comprises anequator line, defining a largest circumference of said inner surface,said inner surface adapted to engage said prosthetic replacement for thecaput femur, and b) said at least one extending portion passes beyondsaid equator line, such that an end portion of said contacting portionof said inner surface extends at least partly along an extension linehaving a smaller circumference than said equator line, and such that aportion of said elongated member can be placed between said extensionline and said equator line, when said medical device is implantedtogether with the prosthetic replacement for the caput femur.
 3. Themedical device according to claim 2, being configured such that saidextension line can be placed dorsal to the equator line, when themedical device is implanted.
 4. The medical device according to claim 2,wherein said at least one extending portion is configured such that itextends circumferentially along said equator line, in a proximalquadrant of the equator line, when the medical device is implanted andthe hip joint is arranged in a defined base position.
 5. The medicaldevice according to claim 2, wherein said at least one extending portionis configured such that it extends circumferentially along said equatorline, in the distal quadrant of the equator line, when the medicaldevice is implanted and the hip joint is arranged in a defined baseposition.
 6. The medical device according to claim 2, wherein said atleast one extending portion comprises two extending portions, and saidtwo extending portions extend circumferentially along said equator line,such that they, when the medical device is implanted and the hip jointis arranged in a defined base position can be placed: distal andproximal to a caput and collum femur center axis CX extending throughthe caput and collum femur, or, proximal and dorsal to the caput andcollum femur center axis CX, or distal and dorsal quadrant to the caputand collum femur center axis CX, or distal, dorsal and proximal to thecaput and collum femur center axis CX.
 7. The medical device accordingto claim 2, wherein at least a first portion of said artificialacetabulum is the at least one extending portion, extending beyond saidequator line, and at least a second portion of said artificialacetabulum is a portion not extending beyond said equator line, whereinsaid second portion circumferentially extends along at least ¼ of saidequator line.
 8. The medical device according to claim 1, wherein saidat least one extending portion is configured such that it can be placeddorsal to a caput and collum femur center axis CX extending through thecaput and collum femur, when the medical device is implanted and the hipjoint is arranged in a defined base position.
 9. The medical deviceaccording to claim 1, wherein said at least one extending portion isconfigured such that it extends circumferentially along said equatorline, dorsal to a coronal pelvis plane PXY, coinciding with a caput andcollum femur center axis CX extending through the caput and collumfemur, and proximal to a horizontal pelvis plane PXZ, being orthogonalto the caput and collum femur center axis CX, when the medical device isimplanted and the hip joint is arranged in a defined base position. 10.The medical device according to claim 1, wherein said at least oneextending portion is configured such that it extends circumferentiallyalong said equator line, dorsal to a coronal pelvis plane PXY,coinciding with a caput and collum femur center axis CX extendingthrough the caput and collum femur, and distal to a horizontal pelvisplane PXZ, being orthogonal to the caput and collum femur center axisCX, when the medical device is implanted and the hip joint is arrangedin a defined base position.
 11. The medical device according to claim 1,wherein said at least one extending portion is configured such that itextends circumferentially along said equator line dorsal to a coronalpelvis plane PXY, coinciding with a caput and collum femur center axisCX extending through the caput and collum femur, and proximal to ahorizontal pelvis plane PXZ, being orthogonal to the caput and collumfemur center axis CX, and at least one further extending portion isconfigured such that it extends dorsal to the coronal pelvis plane PXYand distal to the horizontal pelvis plane PXZ, when the medical deviceis implanted and the hip joint is arranged in a defined base position.12. The medical device according to claim 1, wherein said artificialacetabulum further comprises at least one hole, and wherein said atleast one hole is adapted to receive a fixating member, for fixatingsaid artificial acetabulum to the femoral bone.
 13. The medical deviceaccording to claim 12, wherein at least one of said at least one hole isadapted to receive a screw for fixating said artificial acetabulum tothe femoral bone.
 14. The medical device according claim 1, wherein saidartificial acetabulum is adapted to release the prosthetic replacementfor the caput femur from said artificial acetabulum when a predeterminedstrain is placed on said artificial acetabulum.